This investigation will examine the cell lineages by which precursor cells in the embryo give rise to the diverse set of cell types of the intact organism. In particular, it will assay the progeny of individual avian neural crest cells in situ and in culture. The neural crest is chosen as a model system because it gives rise to diverse derivatives including neurons, pigment cells, glia and cartilage. Furthermore, these cells are experimentally accessible within the embryo and can be easily explanted in tissue culture. Individual neural crest cells or their precursors are labeled by iontophoretic injection of fluorescent lysinated dextran dyes into the cytoplasm. This lineage tracer can only be passed to progeny of the injected cells. Our preliminary results demonstrate that the techniques work and that some trunk neural cells in situ are multipotent. We will extend these preliminary studies by: 1. further characterizing the cell lineage of premigratory truncal, cranial, vagal and lumbosacral neural crest cells. 2. analyzing the developmental potential of already migrating neural crest cells. 3. analyzing the lineage of cells within neural crest- derived ganglia. 4. analyzing the differentiation of clonally related neural crest cells in vitro under various culture conditions. 5. analyzing the lineage of other neural tube cells. These studies will greatly clarify our understanding of the normal differentiation of neural crest cells in situ and give insight into the mechanisms that control both normal development and the abnormal development which results in birth defects.